1. Field of The Invention
The present invention relates to an air/fuel ratio detecting apparatus for an internal combustion engine, which is capable of correcting the error in the measurement of the air/fuel ratio of a mixture supplied for the engine, which is caused by the aged deterioration resulted from the use extending over a long period of time.
2. Description of The Related Art
As is well known, the aged deterioration attends an air/fuel ratio detecting apparatus, which causes the error in the measurement of an air/fuel ratio of a mixture supplied for an internal combustion engine. To improve this, a calibrating method as disclosed in the Japanese Patent Laid-open Publication No. 58-57050 has been proposed, for example. According thereto, the error caused by the aged deterioration is corrected on the basis of an output signal produced by the air/fuel ratio detecting apparatus under the condition that an exhaust pipe, to which the detecting apparatus is attached, is filled with fresh air. However, it is very difficult to bring about such a condition in a short time. In the method of this prior art, unless fresh air perfectly fills the exhaust pipe, the output signal of the detecting apparatus becomes inappropriate for using it as a reference in calibrating the detecting apparatus. In addition, it is also not easy to confirm whether the exhaust pipe has been perfectly filled with fresh air.